This project studies the interrelationships between several neuropeptides (vasopressin, angiotensin II, corticotropin releasing factor and somatostatin) and their role in neuroendocrine regulation. We use animal models of genetic diseases: the Brattleborg rat, which in its homozygous state cannot produce vasopressin, and the spontaneously hypertensive rat. A relationship between angiotensin II, somatostatin and vasopressin can clearly be shown in individual brain nuclei and pituitary gland of Brattleboro rats. Angiotensin II selectively stimulates glucose utilization in the subfornical organ and the posterior pituitary. We have developed new techniques for the localization of angiotensin II receptors in brain nuclei and peripheral organs. We have found that two pituitary neuropeptides are present in fibers originated in the brain: corticotropin-releasing factor (in posterior lobe and intermediate lobe) and somatostatin (in intermediate lobe only). Specific roles for both peptides are postulated in the intermediate pituitary lobe.